From: Douglas Gilbert <dgilbert@interlog.com>
To: bugzilla-daemon@bugzilla.kernel.org, linux-scsi@vger.kernel.org
Cc: Hannes Reinecke <hare@suse.de>
Subject: Re: [Bug 212337] scsi_debug: race at module load and module unload
Date: Thu, 18 Mar 2021 14:32:42 -0400 [thread overview]
Message-ID: <9e060bf1-c676-217d-0608-141b96335676@interlog.com> (raw)
In-Reply-To: <bug-212337-11613-BobYNlW3hA@https.bugzilla.kernel.org/>
On 2021-03-18 1:38 p.m., bugzilla-daemon@bugzilla.kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=212337
>
> Luis Chamberlain (mcgrof@kernel.org) changed:
>
> What |Removed |Added
> ----------------------------------------------------------------------------
> Status|NEW |RESOLVED
> Resolution|--- |WILL_NOT_FIX
>
> --- Comment #1 from Luis Chamberlain (mcgrof@kernel.org) ---
>
> At first glance this might seem like a problem with scsi's async probe, and so
> one might believe disabling CONFIG_SCSI_SCAN_ASYNC could help, however it does
> not. Linux scsi doesn't have semantics to allow only one driver to prefer to
> probe asynchronously, but we can shoe-horn this in as follows:
>
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 3cdeaeb92933..d970050ae866 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -857,6 +857,8 @@ static const int device_qfull_result =
>
> static const int condition_met_result = SAM_STAT_CONDITION_MET;
>
> +MODULE_IMPORT_NS(SCSI_PRIVATE);
> +int scsi_complete_async_scans(void);
>
> /* Only do the extra work involved in logical block provisioning if one or
> * more of the lbpu, lbpws or lbpws10 parameters are given and we are doing
> @@ -6851,6 +6853,7 @@ static int __init scsi_debug_init(void)
> }
> }
> }
> + scsi_complete_async_scans();
> if (sdebug_verbose)
> pr_info("built %d host(s)\n", sdebug_num_hosts);
>
> Even with this present though we still have he refcnt issue. A better way to
> see what is going on is to trace the kernel module calls after boot and see why
> perhaps certain refcounts for the module are high at times and why they are not
> in most other cases.
Hi,
Interesting analysis. There have been many changes to the scsi_debug driver
during the last 6 months, but none that I can remember in module
initialization area. Do you think this is a problem introduced by those
changes or may it have been there for a longer period? Could it be that
the scsi_debug driver is exposing the async nature of the scanning code.
Of course, commencing device teardown during an async scan is stress testing
that code. It would be an improvement IMO, if rmmod alerted the module
in question when it rejects a removal attempt with "device busy".
To stop any higher levels setting up SCSI devices before the async scans
are complete, the scsi_debug can set TEST UNIT READY to return an error
along the lines of: not ready, device in process of becoming ready
BTW that is what real devices do, but scsi_debug does not do that by default.
The scsi_debug module option that is already in place is:
tur_ms_to_ready: TEST UNIT READY millisecs before initial good status (def=0)
So it's just a fixed delay at the moment. Perhaps you could experiment with that
option to see if it improves things.
The post is cc-ed to Hannes Reinecke who does most of the work in the async
scanning area.
Doug Gilbert
> Enable module tracing
>
> # for i in $(sudo find /sys/kernel/debug/tracing/events/module/ -name
> "enable"); do echo 1 > $i; done
>
> Run a loop to test modprobe / rmmod, and fail if either fails. In this case
> let's assume a success of rmmod once and then a failure on the second removal.
> We get the following ftrace, I'll provide some comments in areas where this may
> be useful
>
> # cat trace /sys/kernel/tracing
> # tracer: nop
> #
> # entries-in-buffer/entries-written: 355/355 #P:8
> #
> # _-----=> irqs-off
> # / _----=> need-resched
> # | / _---=> hardirq/softirq
> # || / _--=> preempt-depth
> # ||| / delay
> # TASK-PID CPU# |||| TIMESTAMP FUNCTION
> # | | | |||| | |
> modprobe-902 [005] .... 45.731217: module_get: scsi_mod
> call_site=resolve_symbol refcnt=6
> modprobe-902 [005] .... 45.732844: module_load: scsi_debug E
> modprobe-902 [005] .... 45.732850: module_get: scsi_debug
> call_site=sdebug_add_store [scsi_debug] refcnt=3
> modprobe-902 [005] .... 45.733589: module_put: scsi_debug
> call_site=sdebug_add_store [scsi_debug] refcnt=2
> modprobe-902 [005] .... 45.733963: module_get: scsi_debug
> call_site=sdebug_driver_probe [scsi_debug] refcnt=3
> modprobe-902 [001] .... 45.738246: module_put: scsi_debug
> call_site=sdebug_driver_probe [scsi_debug] refcnt=2
> kworker/u16:3-173 [002] .... 45.738790: module_get: scsi_debug
> call_site=scsi_debug_slave_alloc [scsi_debug] refcnt=3
> kworker/u16:3-173 [002] .... 45.739943: module_put: scsi_debug
> call_site=scsi_debug_slave_alloc [scsi_debug] refcnt=2
> kworker/u16:3-173 [007] .... 45.748555: module_get: scsi_debug
> call_site=scsi_debug_slave_configure [scsi_debug] refcnt=3
> kworker/u16:3-173 [007] .N.. 45.749962: module_put: scsi_debug
> call_site=scsi_debug_slave_configure [scsi_debug] refcnt=2
> kworker/u16:3-173 [000] d... 45.766235: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/u16:3-173 [000] d... 45.769197: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=4
> kworker/u16:3-173 [000] .... 45.769197: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=3
> kworker/u16:3-173 [000] .... 45.769198: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=2
> kworker/u16:3-173 [000] d... 45.769199: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/u16:3-173 [000] .... 45.769785: module_put: scsi_debug
> call_site=__scsi_iterate_devices [scsi_mod] refcnt=2
> modprobe-902 [001] .... 45.773492: module_put: scsi_debug
> call_site=do_init_module refcnt=1
>
> So we can escape initialization early in one case as sg module is not yet
> available.
>
> systemd-udevd-907 [001] .... 45.773818: module_get: scsi_mod
> call_site=resolve_symbol refcnt=7
> systemd-udevd-907 [001] .... 45.774708: module_load: sg E
> systemd-udevd-907 [001] .... 45.776173: module_put: sg
> call_site=do_init_module refcnt=1
> systemd-udevd-907 [001] .... 45.778501: module_get: scsi_mod
> call_site=resolve_symbol refcnt=8
> systemd-udevd-907 [001] .... 45.778569: module_get: t10_pi
> call_site=resolve_symbol refcnt=3
> systemd-udevd-907 [001] .... 45.779733: module_load: sd_mod E
> systemd-udevd-907 [001] .... 45.828660: module_put: sd_mod
> call_site=do_init_module refcnt=1
> rmmod-908 [003] .... 45.921238: module_free: scsi_debug
>
> We remove the scsi_debug module here fine before systemd-udevd has opened the
> device.
>
> rmmod-908 [003] .... 45.921442: module_put: scsi_mod
> call_site=module_unload_free refcnt=7
> modprobe-914 [006] .... 45.944276: module_get: scsi_mod
> call_site=resolve_symbol refcnt=8
>
> modprobe-914 [006] .... 45.945820: module_load: scsi_debug E
> modprobe-914 [006] .... 45.945825: module_get: scsi_debug
> call_site=sdebug_add_store [scsi_debug] refcnt=3
> modprobe-914 [006] .... 45.946553: module_put: scsi_debug
> call_site=sdebug_add_store [scsi_debug] refcnt=2
> modprobe-914 [006] .... 45.947044: module_get: scsi_debug
> call_site=sdebug_driver_probe [scsi_debug] refcnt=3
> modprobe-914 [006] .... 45.952509: module_put: scsi_debug
> call_site=sdebug_driver_probe [scsi_debug] refcnt=2
> kworker/u16:3-173 [006] .... 45.953257: module_get: scsi_debug
> call_site=scsi_debug_slave_alloc [scsi_debug] refcnt=3
> kworker/u16:3-173 [006] .N.. 45.954616: module_put: scsi_debug
> call_site=scsi_debug_slave_alloc [scsi_debug] refcnt=2
> kworker/u16:3-173 [006] .... 45.964402: module_get: scsi_debug
> call_site=scsi_debug_slave_configure [scsi_debug] refcnt=3
> kworker/u16:3-173 [006] .N.. 45.965695: module_put: scsi_debug
> call_site=scsi_debug_slave_configure [scsi_debug] refcnt=2
> kworker/u16:3-173 [005] d... 46.213491: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/u16:3-173 [005] d... 46.215346: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=4
> kworker/u16:3-173 [005] .... 46.215347: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=3
> kworker/u16:3-173 [005] .... 46.215348: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=2
> kworker/u16:3-173 [005] d... 46.215350: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/u16:3-173 [005] .... 46.220794: module_put: scsi_debug
> call_site=__scsi_iterate_devices [scsi_mod] refcnt=2
> kworker/u16:4-174 [004] .... 46.224892: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.224893: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.224894: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.228906: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.228907: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.228907: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.230926: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.230926: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.230927: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.234937: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.234938: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.234938: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .N.. 46.246062: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .N.. 46.246064: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .N.. 46.246065: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.250071: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.250072: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.250072: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.252943: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.252943: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.252944: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.256956: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.256957: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.256957: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.258547: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.258547: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.258548: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.262558: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.262558: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.262559: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .N.. 46.266484: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .N.. 46.266484: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .N.. 46.266485: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.270492: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.270492: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.270493: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.272381: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.272382: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.272382: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.276393: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.276393: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.276394: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.278258: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> kworker/u16:4-174 [004] .... 46.278259: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [004] .... 46.278259: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.282269: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=4
> <idle>-0 [004] d.h. 46.282270: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> <idle>-0 [004] d.h. 46.282270: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=2
> kworker/u16:4-174 [004] .... 46.374616: module_get: sd_mod
> call_site=blkdev_get_no_open refcnt=2
> kworker/u16:4-174 [004] .... 46.374617: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/4:1H-189 [004] .... 46.376457: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/4:1H-189 [004] .... 46.376457: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/4:1H-189 [004] .... 46.376458: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/4:1-62 [004] d.h. 46.380469: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> kworker/4:1-62 [004] d.h. 46.380470: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/4:1-62 [004] d.h. 46.380470: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> kworker/0:1H-89 [000] .... 46.383278: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/0:1H-89 [000] .... 46.383279: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/0:1H-89 [000] .... 46.383280: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.387291: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [000] d.h. 46.387292: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.387292: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> kworker/0:1H-89 [000] .... 46.389080: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/0:1H-89 [000] .... 46.389081: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/0:1H-89 [000] .... 46.389081: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.393090: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [000] d.h. 46.393091: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.393091: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> kworker/u16:4-174 [000] .... 46.393170: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=2
> kworker/u16:4-174 [000] .... 46.393171: module_put: sd_mod
> call_site=blkdev_put refcnt=1
> systemd-udevd-907 [003] .... 46.393476: module_get: sd_mod
> call_site=blkdev_get_no_open refcnt=2
> systemd-udevd-907 [003] .... 46.393477: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=3
> kworker/u16:4-174 [000] .... 46.395771: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.395772: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.395773: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.399789: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [000] d.h. 46.399790: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.399790: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> kworker/u16:4-174 [000] .... 46.402067: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.402068: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.402069: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.406078: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [000] d.h. 46.406079: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [000] d.h. 46.406079: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> multipath-926 [005] .... 46.409545: module_get: sd_mod
> call_site=blkdev_get_no_open refcnt=3
> multipath-926 [005] .... 46.409547: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=4
> multipath-926 [005] .... 46.409649: module_get: dm_mod
> call_site=misc_open refcnt=2
> multipath-926 [005] .... 46.409773: module_put: dm_mod
> call_site=__fput refcnt=1
> multipath-926 [005] .... 46.410096: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=3
> multipath-926 [005] .... 46.410097: module_put: sd_mod
> call_site=blkdev_put refcnt=2
> systemd-udevd-907 [003] .... 46.410279: module_get: sd_mod
> call_site=blkdev_get_no_open refcnt=3
> systemd-udevd-907 [003] .... 46.410280: module_get: scsi_debug
> call_site=scsi_device_get [scsi_mod] refcnt=4
> systemd-udevd-907 [003] .... 46.413760: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.413760: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.413760: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.417764: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.417764: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.417764: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.438981: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.438981: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.438982: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.439875: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.439875: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.439876: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.442992: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.442993: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.442994: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.443880: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.443880: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.443880: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.444546: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.444547: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.444548: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.445450: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.445450: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.445450: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.448558: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.448559: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.448559: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.449452: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.449453: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.449453: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.450135: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.450136: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.450136: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.451003: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.451003: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.451004: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.454147: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.454148: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.454148: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.455008: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.455008: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.455008: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.455910: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.455910: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.455911: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.456804: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.456805: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.456805: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.459920: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.459921: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.459921: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.460808: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.460809: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.460809: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.461664: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.461664: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.461665: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.462544: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.462545: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.462545: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.465674: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.465675: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.465675: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.466547: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.466548: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.466548: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> kworker/u16:4-174 [000] .... 46.467413: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> kworker/u16:4-174 [000] .... 46.467413: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> kworker/u16:4-174 [000] .... 46.467414: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.468319: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.468319: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=7
> systemd-udevd-907 [003] .... 46.468319: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.471425: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=7
> <idle>-0 [000] d.h. 46.471426: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=6
> <idle>-0 [000] d.h. 46.471426: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.472322: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=6
> <idle>-0 [003] d.h. 46.472323: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.472323: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.473538: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.473538: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=6
> systemd-udevd-907 [003] .... 46.473538: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> modprobe-914 [006] .... 46.474870: module_put: scsi_debug
> call_site=do_init_module refcnt=4
>
> <idle>-0 [003] d.h. 46.477540: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.477541: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.477541: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.478789: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.478789: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.478790: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.482795: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.482796: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.482796: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.483713: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.483713: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.483714: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.487723: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.487723: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.487724: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.488736: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.488737: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.488737: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.492740: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.492741: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.492741: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.493621: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.493621: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.493621: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.497627: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.497628: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.497628: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.498631: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.498632: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.498632: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.502634: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.502635: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.502635: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.503506: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.503507: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.503507: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.507513: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.507513: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.507514: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.508540: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.508540: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.508541: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.512543: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.512543: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.512543: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.513421: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.513421: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.513421: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.517425: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.517425: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.517425: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.518504: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.518505: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.518505: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.522509: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.522509: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.522509: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.523418: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.523418: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.523418: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.527420: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.527420: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.527420: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.528436: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.528437: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.528437: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.532440: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.532441: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.532441: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.533324: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.533324: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.533324: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.537329: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.537330: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.537330: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.538373: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.538374: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.538374: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.542376: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.542377: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.542377: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.543259: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.543260: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.543260: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.547268: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.547269: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.547269: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.548246: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.548246: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.548247: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.552251: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.552251: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.552251: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.553258: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.553258: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.553258: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.557264: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.557264: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.557264: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.558294: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.558295: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.558295: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.562299: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.562300: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.562300: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.563242: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.563242: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.563242: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.567248: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.567248: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.567249: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.568196: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.568196: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.568197: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.572204: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.572205: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.572205: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.573125: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.573125: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.573126: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.577132: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.577133: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.577133: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.578070: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.578071: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.578071: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.582079: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.582080: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.582080: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.583013: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> systemd-udevd-907 [003] .... 46.583013: module_get: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=5
> systemd-udevd-907 [003] .... 46.583014: module_put: scsi_debug
> call_site=schedule_resp [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.587025: module_get: scsi_debug
> call_site=sdebug_q_cmd_complete [scsi_debug] refcnt=5
> <idle>-0 [003] d.h. 46.587026: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=4
> <idle>-0 [003] d.h. 46.587026: module_put: scsi_debug
> call_site=sdebug_q_cmd_hrt_complete [scsi_debug] refcnt=3
> systemd-udevd-907 [003] .... 46.587080: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=2
> systemd-udevd-907 [003] .... 46.587081: module_put: sd_mod
> call_site=blkdev_put refcnt=2
> systemd-udevd-907 [003] .... 46.588154: module_put: scsi_debug
> call_site=scsi_device_put [scsi_mod] refcnt=1
> systemd-udevd-907 [003] .... 46.588155: module_put: sd_mod
> call_site=blkdev_put refcnt=1
>
> One might be at first motivated to implment sledge hammers as follows:
>
> static void sdebug_wait_empty_num_in_q(void)
> {
> struct sdebug_host_info *sdbg_host;
> struct Scsi_Host *shost;
> struct scsi_device *sdev;
> struct sdebug_dev_info *devip;
> int count, max_wait = 5, k;
> bool busy;
>
> while (true) {
> busy = false;
> spin_lock(&sdebug_host_list_lock);
> list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
> shost = sdbg_host->shost;
> shost_for_each_device(sdev, shost) {
> devip = (struct sdebug_dev_info
> *)sdev->hostdata;
> if (atomic_read(&devip->num_in_q) != 0)
> busy = true;
> k = find_first_bit(devip->uas_bm,
> SDEBUG_NUM_UAS);
> if (k != SDEBUG_NUM_UAS)
> busy = true;
> }
> }
> spin_unlock(&sdebug_host_list_lock);
> if (!busy || count >= max_wait) {
> break;
> }
> ssleep(1);
> count++;
> }
> }
>
> /* Waits for all pending commands to complete. */
> static void wait_all_queued(void)
> {
> int j, k;
> struct sdebug_queue *sqp;
> bool busy;
>
> while (true) {
> busy = false;
> for (j = 0, sqp = sdebug_q_arr; j < submit_queues; ++j, ++sqp)
> {
> k = find_first_bit(sqp->in_use_bm, sdebug_max_queue);
> if (k != sdebug_max_queue)
> busy = true;
> }
> if (!busy)
> break;
> ssleep(1);
> }
> }
>
> static void sync_qc_helper(struct sdebug_defer *sd_dp,
> enum sdeb_defer_type defer_t)
> {
> if (!sd_dp)
> return;
> if (defer_t == SDEB_DEFER_HRT) {
> hrtimer_forward_now(&sd_dp->hrt, 2 *
> hrtimer_get_remaining(&sd_dp->hrt));
> } else if (defer_t == SDEB_DEFER_WQ) {
> flush_work(&sd_dp->ew.work);
> }
> }
>
> static void scsi_debug_sync_queued_cmnd(void)
> {
> unsigned long iflags;
> int j, k, qmax, r_qmax;
> enum sdeb_defer_type l_defer_t;
> struct sdebug_queue *sqp;
> struct sdebug_queued_cmd *sqcp;
> struct sdebug_defer *sd_dp;
>
> for (j = 0, sqp = sdebug_q_arr; j < submit_queues; ++j, ++sqp) {
> spin_lock_irqsave(&sqp->qc_lock, iflags);
> qmax = sdebug_max_queue;
> r_qmax = atomic_read(&retired_max_queue);
> if (r_qmax > qmax)
> qmax = r_qmax;
> for (k = 0; k < qmax; ++k) {
> if (test_bit(k, sqp->in_use_bm)) {
> sqcp = &sqp->qc_arr[k];
> sd_dp = sqcp->sd_dp;
> if (sd_dp)
> l_defer_t = sd_dp->defer_t;
> else
> l_defer_t = SDEB_DEFER_NONE;
> spin_unlock_irqrestore(&sqp->qc_lock, iflags);
> sync_qc_helper(sd_dp, l_defer_t);
> spin_lock_irqsave(&sqp->qc_lock, iflags);
> }
> }
> spin_unlock_irqrestore(&sqp->qc_lock, iflags);
> }
> }
>
> static void wait_for_ready(void)
> {
> struct scsi_sense_hdr sense_hdr;
> struct sdebug_host_info *sdbg_host;
> struct Scsi_Host *shost;
> struct scsi_device *sdev;
> int ret;
> bool all_ready;
>
> spin_lock(&sdebug_host_list_lock);
> while (true) {
> all_ready = true;
> list_for_each_entry(sdbg_host, &sdebug_host_list, host_list) {
> shost = sdbg_host->shost;
> shost_for_each_device(sdev, shost) {
> ret = scsi_internal_device_block_nowait(sdev);
> if (ret)
> all_ready = false;
> ret = scsi_internal_device_unblock_nowait(sdev,
> SDEV_RUNNING);
> if (ret)
> all_ready = false;
> ret = scsi_test_unit_ready(sdev, 5 * HZ, 100,
> &sense_hdr);
> if (ret != 0)
> all_ready = false;
> }
> }
> if (all_ready)
> break;
> ssleep(1);
> }
> spin_unlock(&sdebug_host_list_lock);
> }
>
> And use these on scsi_debug_init() but that does not suffice, and the reason is
> that userspace can open the scsi devices after initialization, namely in this
> case we see evidence of userspace processes such as systemd-udevd and multipath
> which will try to open the device.
>
> There are a few solutions possible, using sync, or sg_sync is not one of them
> as we have to ensure we have no userspace application accessing the devices
> still.
>
> You can use lsof for this purpose. Below is an example script which can be
> used.
>
> #!/bin/bash
>
> LOOP=1
>
> while true; do
> modprobe scsi_debug
> if [[ $? -ne 0 ]]; then
> echo "scsi_debug modprobe failed at count $LOOP"
> exit 1
> fi
> while true; do
> # Let other modules which scsi_debug depends on like sg
> # and t10_pi load first to ensure any commands sent to
> # the device are sent.
> sleep 1
>
> # Now wait until userspace such as systemd-udevd and multipath
> # are done inspecting the newly exposed devices.
> COUNT=$(lsof /dev/sda | wc -l)
> if [[ $COUNT -ne 0 ]]; then
> echo "Sleeping ..."
> sleep 1;
> fi
> break
> done
> # Now you are safe to use scsi_debug exposed devices.
>
> # You are also free to remove it.
> rmmod scsi_debug
> if [[ $? -ne 0 ]]; then
> echo "scsi_debug rmmod failed at count $LOOP"
> exit 1
> else
> echo "Loop $LOOP: OK!"
> fi
> let LOOP=$LOOP+1
> done
>
>
> Marking this bug as resolved and won't fix as this should hopefully suffice to
> document why we can't wait on scsi_debug_init() to fix this issue, and it must
> be addressed in userspace.
>
next prev parent reply other threads:[~2021-03-18 18:34 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 17:09 [Bug 212337] New: scsi_debug: race at module load and module unload bugzilla-daemon
2021-03-18 17:38 ` [Bug 212337] " bugzilla-daemon
2021-03-18 18:32 ` Douglas Gilbert [this message]
2021-03-18 17:43 ` bugzilla-daemon
2021-03-18 18:42 ` bugzilla-daemon
2021-03-18 19:14 ` bugzilla-daemon
2021-03-18 21:00 ` Douglas Gilbert
2021-03-18 19:20 ` bugzilla-daemon
2021-03-18 19:22 ` bugzilla-daemon
2021-03-18 19:57 ` bugzilla-daemon
2021-03-18 21:00 ` bugzilla-daemon
2021-03-22 16:23 ` bugzilla-daemon
2021-03-23 0:37 ` Douglas Gilbert
2021-03-22 18:21 ` bugzilla-daemon
2021-03-22 18:31 ` bugzilla-daemon
2021-03-23 0:38 ` bugzilla-daemon
2021-05-04 21:18 ` bugzilla-daemon
2021-05-05 15:57 ` Douglas Gilbert
2021-05-04 21:22 ` bugzilla-daemon
2021-05-05 16:06 ` bugzilla-daemon
2021-05-07 18:25 ` bugzilla-daemon
2021-05-07 20:46 ` Douglas Gilbert
2021-05-07 20:46 ` bugzilla-daemon
2021-05-07 22:37 ` bugzilla-daemon
2021-05-07 22:46 ` bugzilla-daemon
2021-07-27 19:27 ` bugzilla-daemon
2021-07-30 20:31 ` bugzilla-daemon
2021-08-10 5:19 ` bugzilla-daemon
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